The present invention relates to a detection mechanism for detecting the standard position of the cutting direction of a cutting blade mounted to a cutting machine such as a dicing machine, or the time of exchanging the cutting blade and a chipped cutting blade.
A semiconductor wafer or the like is generally cut by a precision cutting machine called xe2x80x9cdicing machinexe2x80x9d. The dicing machine cuts a workpiece of a semiconductor wafer or the like with a rotating cutting blade. This cutting blade is worn down by its use and its diameter decreases. In the dicing machine, therefore, the standard position of the cutting direction of the cutting blade needs to be adjusted to cope with a reduction in the diameter of the cutting blade and hence, it has a cutting blade detection mechanism for detecting the standard position. The dicing machine also has a cutting blade detection mechanism for detecting the time of exchanging the cutting blade whose diameter is reduced by abrasion and a chipped cutting blade.
The above cutting blade detection mechanism comprises a blade passing gap into which the cutting blade passes, and a light emitting means and a light receiving means both of which face the blade passing gap. In this cutting blade detection mechanism, a light emitted by the light emitting means is received by the light receiving means and the state of the cutting blade located in the blade passing gap between the light emitting means and the light receiving means is detected by converting the amount of light received by the light receiving means into a voltage corresponding to the amount of light. The cutting blade detection mechanism for detecting the standard position of the cutting direction of the cutting blade is disposed on a workpiece holding means for holding a workpiece, and when the cutting blade is moved in a cutting direction so as to gradually pass into the blade passing gap and the voltage corresponding to the amount of light received by the light receiving means reaches a predetermined value, the standard position of the cutting direction of the cutting blade is determined. That is, when the cutting blade is caused to gradually pass into the blade passing gap, the amount of light received by the light receiving means gradually decreases and the value of voltage falls. When the value of voltage reaches a predetermined value, the standard position of the cutting direction of the cutting blade is determined as a position where the cutting blade comes in contact with the top surface of the workpiece holding means, for instance. Meanwhile, the cutting blade detection mechanism for detecting the time of exchanging the cutting blade and a chipped cutting blade is disposed on a spindle unit having the cutting blade. As the cutting blade is worn down, the amount of light intercepted by the cutting blade located between the light emitting means and the light receiving means decreases. In this case, the value of detection voltage gradually rises from the time when the cutting blade has been exchanged and it reaches a predetermined value, the cutting blade detection mechanism indicates the time of exchanging the cutting blade. Further, the above cutting blade detection mechanism judges occurrence of a chipped cutting blade and indicates the time of exchanging the cutting blade since it shows the voltage value exceeding a predetermined value intermittently when the cutting blade is chipped.
There occurs, however, a case where the above cutting blade detection mechanisms can not detect the state of the cutting blade located in the blade passing gap between the light emitting means and the light receiving means because contamination scattered at the time when the workpiece is cut with the cutting blade is adhered to the surfaces of the light emitting means and the light receiving means. That is, when the chippings are adhered to the surface of the light emitting means, the amount of light emitted toward the light receiving means decreases and when the chippings are adhered to the surface of the light receiving means, the amount of light received decreases. Therefore, the state of the cutting blade located in the blade passing gap between the light emitting means and the light receiving means, that is, the standard position of the cutting direction of the cutting blade or the time of exchanging the cutting blade and a chipped cutting blade cannot be detected accurately.
It is an object of the present invention to provide a cutting blade detection mechanism for a cutting machine that can detect the state of a cutting blade always with stability and high accuracy.
To attain the above object, according to the present invention, there is provided a cutting blade detection mechanism for a cutting machine, which has a blade passing gap into which a cutting blade for cutting a workpiece held by a workpiece holding means for holding the workpiece passes and a light emitting means and a light receiving means both of which face the blade passing gap, wherein the mechanism comprises cleaning water supply nozzles for supplying cleaning water to the end surfaces of the light emitting means and the light receiving means and air supply nozzles for supplying air to the end surfaces of the light emitting means and the light receiving means, respectively.
It is desired that the openings of the air supply nozzles should be arranged adjacent to the light emitting means and the light receiving means and that the openings of the cleaning water supply nozzles should be arranged behind the openings of the air supply nozzles, respectively.